Aromatic peroxy acids may be prepared from the reaction of hydrogen peroxide and aromatic acids by using a reaction medium of alkane sulfonic acid as described in U.S. Pat. No. 3,143,562.
Inherent in the reaction of aromatic acids and hydrogen peroxide is the formation of by-product water, together with water accompanying the reagents, notably the hydrogen peroxide reactant (hydrogen peroxide is commercially available at 90 weight percent or less concentration). Generally, the best yields of peroxy acids are favored by minimizing the concentration of water in the reaction medium. Thus, it is important to process the alkane sulfonic acid used as reaction medium to remove the greater portion of contained water. It is also economically and environmentally desirable to recycle the alkane sulfonic acid.
Alkane sulfonic acids such as methane sulfonic acid have high boiling points which make simple distillative dehydration unattractive because of attendant decomposition. Recourse to distillation at subatmospheric pressures is usually required to separate water from aqueous alkane sulfonic acid solutions without undue decomposition where reconstitution is required.